CircuitPython midi, usb.core and max3421 blocking issues

max3421_midi_test.py

# demonstrate blocking of usb.core.Device.read() 
#  4 May 2024 - @todbot and @jedgarpark
"""
This sketch demonstrates how `device.read()` blocks infinitely, which is different from established behavior. 

The normal semantics of `device.read()` when using either `busio.UART` or `usb_midi.PortIn`
is that the read() does not noticably block if a `timeout` is given. 
(Explicitly in the constructor of `busio.UART` and apparently implicitly in just how `usb_midi` works)

But for the `usb.core.Device` that is returned (as demo'd below), the `device.read()` blocks forever. 
Using `asyncio` or `select` does not help with this. 

There is a non-standard `timeout` argument to the `usb.core.Device.read()` 
and `usb.core.Device.write()` methods, but when specifying a timeout on `.read()`,
an unattributed `usb.core.USBError` is thrown, instead of the expected return value of None or 0. 
Since the exception is unattributed, there's no wayt to distinguish a read timeout 
from a device unplug or other USB error.
"""

import time
import board
import usb
import max3421e

import adafruit_usb_host_midi

spi = board.SPI()
cs = board.D10
irq = board.D9

host_chip = max3421e.Max3421E(spi, chip_select=cs, irq=irq)

while True:
   midi_usb_device = None
   for device in usb.core.find(find_all=True):
      try:
         midi_usb_device = adafruit_usb_host_midi.MIDI(device)
         print("Found vid/pid %04x/%04x" % (device.idVendor, device.idProduct),
               device.manufacturer, device.product)
      except ValueError:
         print("bad device:", device)

      while True:
         print("this should print continuously")
         time.sleep(0.1)
         b = midi_usb_device.read(1)
         if b:
            print("should only print when data received:",b)